Structures, Materials, and Processes at the Electrode-to-Tissue Interface

Abstract

This chapter reviews the basic concepts of neural stimulation along with safety considerations for both the electrode and tissue. The section on electrode–electrolyte interface describes the basic mechanism of charge injection at the interface introducing the reader to the electrode double layer. The use of circuit models to represent the physical processes at the interface and in the bulk tissue is discussed. The next section provides a detailed description of the biopotential electrode along with measurement techniques used in electrode characterization. Following this, an overview of popular electrode materials for neural stimulation is provided for the reader. These include conventional materials such as platinum and iridium oxide, as well as newer materials like conducting polymers and carbon nanotubes. The next section reviews the concept of extracellular stimulation introducing the reader to Goldman Equation used to describe the membrane potential. Finally the section dedicated to safe stimulation of tissue describes the mechanisms of neural injury and parameters considered to ensure safe neural stimulation. Special emphasis is placed on safety studies of retinal stimulation.